From the beginning of recorded history, most seating surfaces have been hard, but these were eventually followed by seats constructed of resilient material. In recent years, flexibility seating called ergonomic has been evolved. This evolution now continues with a lumbro-sacral seating orthosis in accordance with the instant invention, which will be described in detail hereinafter.
The art of designing body supports, in the nature of chairs and sofas having posterior and lumbar supporting portions, has thus far taken into consideration man's need to have a comfortable and flexible support that continuously conforms to different body positions. For example, chairs and sofas are known to be constructed from posterior and lumbar supporting assemblies consisting generally of a frame having a plurality of springs, a cushion or pad which rests on the springs, and an upholstery cover. These assemblies, although flexible due to their spring construction, assume a predetermined fixed shape which requires that for maximum comfort, persons using such furniture must adjust their body positions relative to these assemblies.
Inasmuch as chairs and sofas are a vital part of man's work and leisure environment, there is a distinct need for providing a body support which is constructed to continuously conform to man's different body positions in order to provide maximum comfort. Thus from hard seating and resilient seating, the next generation, called ergonomic seating, evolved.
There are many ergonomic supports in the nature of chairs, sofas and the like which include flexible and resilient supporting portions which conform to the body to provide comfort. All of these posterior and lumbar supporting sitting surfaces, whether contoured or non-planar, have the ability to form a plurality of cantilevers which automatically adjust and conform to human body movement without mechanical parts, as opposed to adjusting the human body to conform to the supporting portion of the seating surface.
Various ergonomic seats have been proposed for posterior and lumbar supporting assemblies which are designed to possess increased flexibility while providing body support. Such structures are known for example, from U.S. Pat. No. 4,502,731 to Snider, U.S. Pat. No. 4,418,958 to Watkin, U.S. Pat. No. 5,123,702 to Caruso, U.S. Pat. No. 5,076,646 to Matte, U.S. Pat. No. 4,660,887 to Fleming et al, and U.S. Pat. No. 3,389,936 to Drabert. However, each of these structures merely provide an assembly having a plurality of openings to increase flexibility. They also are designed in a manner which permits their continuous adjustment in conforming to different body positions to maximize comfort.
The art of designing a body support to provide maximum comfort has reached a very high level of achievement, but in providing this comfort, a hidden problem has arisen. Although these flexible, conforming, comfortable, ergonomic seating devices are an improvement over hard wooden or resilient seating surfaces, the injury to the back has increased dramatically after the advent of such ergonomic seating. The forces of gravity once felt by the sitting bones (ischial tuberosities) have been transferred up into the pelvis and spine and onto the thigh muscles and gluteal muscles.
None of these various approaches to maximizing comfort through increased flexibility and conforming to different body position apparently foresaw that the reduced pressure on the ischial tuberosities would transfer the pressure to the spine and pelvis. Nor can these flexible ergonomic seats promote what is being called the "loose pack position" of the spine or restrict gluteal spreading. The "loose pack position" of the spine in a seated position is being widely accepted by orthopedists and physical therapists as the correct lordotic curve for a seated person. This is diametrically in contrast with the teachings that ergonomic seat designers have been using prior to this time. These teachings can be found in U.S. Pat. No. 4,660,887 to Fleming et al, and in U.S. Pat. No. 4,418,958 to Watkin. A significant quotation from the Watkin patent is as follows:
"It is desirable that a chair should be shaped to provide support for the spine and thighs of someone sitting on the chair so that the spine is supported in the orthopedically preferred position. This position is described in British patent specification No. 1,294,091 and in the brochure `S Range` published in the United Kingdom by Arenson International Limited of St. Albans. Ideally, the sitter's spine should be supported in an approximately vertical elongate `S` shape whose curves define a plane transverse to the back support of the chair, the lower curve being concave to the back support and being defined by the lumbar and lower thoracic vertebrae while the upper curve is convex and is defined by the upper thoracic and cervical vertebrae . . . . It is also desirable that pressure on the ischial tuberosities of the sitter be reduced. Support of the spine in the `S` shape achieves this to some extent by transferring some of the load on the ischial tuberosities to the underside of the thighs."
With regard to the teaching of transferring pressures from the ischial tuberosities to the thighs and gluteus muscles, as a preferred ergonomic benefit, it is now understood that gluteal spreading, commonly known as "secretary spread" is as injurious to the pelvis and spine as incorrect posture. The anthropometric measurement system for ergonomic seating does not teach gluteal cupping as does the instant invention. No matter how comfortable an ergonomic seating device is, continuous sitting on anthropometrically measured "S range" seating devices will in most humans result in repetitive stress injuries to the back.
Likewise, none of these support assemblies restrict gluteal spreading, medically known as gluteal flexion, sufficiently to shut off the trigger response of the sacro-coccygeal ligaments or prevent the uneven pressure on the pelvic ligaments. Continual spreading (flexion) of the gluteal muscles and flexion of the pelvis bones have been found to result in repetitive stress injuries to the pelvic ligaments, hip joints and sacro-coccygeal ligaments.
There are other known portable collapsible or stationary ergonomic support structures that purport to provide sufficient ergonomic support. These structures shift and assume different body positions in an effort to provide an effectively comfortable ergonomic support to the entire soft tissue of the human body. Such structures are known, for example, in U.S. Pat. No. 3,138,404 to Newton, U.S. Pat. No. 2,551,819 to Wing, U.S. Pat. No. 3,422,938 to Worcester, U.S. Pat. No. 4,533,174 to Fleishman, U.S. Pat. No. 4,202,581 to Fleischman, U.S. Pat. No. 2,663,359 to Wood, U.S. Pat. No. 2,380,102 to Farmer, U.S. Pat. No. 3,422,938; U.S. Pat. No. 4,435,015 to Trotman et al, U.S. Pat. No. 3,389,936 to Drabert and U.S. Pat. No. 3,712,670 to Svehla et al.
No matter how comfortable a portable or stationary ergonomic seating device appears to be, without an individual's spine maintaining a "loose pack position," these portable ergonomic "S range" contour seating devices will in most humans result in repetitive stress injuries to the back.
It can therefore be appreciated that there has been an unsolved need for a portable lumbral sacral sitting orthosis that is distinctly different from known portable or stationary ergonomic chairs and the like. As well be seen in detail hereinafter, my novel design involves a sitting device that corrects posture to a "loose pack position," restricting the flexion of gluteal spreading. It is sincerely believed that no other sitting surface has addressed this novel feature, whether ergonomic, flexible, fixed shaped, portable or stationary.